In recent years, with the worldwide explosive demand for a smart phone, a wireless data usage has rapidly increased. In particular according to a recent report (Cisco VNI 2013), 80% of radio traffic has been generated indoor. Therefore, telecommunication service providers have born a burden of continuously investing mobile communication equipment in order to efficiently meet the demand for the radio traffic indoor, which has explosively increased.
Therefore, public attentions have concentrated on a radio over fiber (RoF) interlocking ultrahigh-frequency communication with an ultrahigh-speed optical communication network, which enables a large-capacity multimedia telecommunication service by joining a wired communication technique and a wireless communication technique.
The RoF technique has a lot of advantages such as achievement of a broadband of a channel capacity, low cost, low power, easy equipment installation and operation management by using both the optical communication technique and the wireless technique. In particular, a distributed antenna system (DAS) which is one example of the RoF technique provides an appropriate solution for an ultrahigh radio multimedia service in outdoor spaces such as an underground tunnel, a narrow street, and a highway as well as indoor spaces such as an airport terminal or a shopping center and a large-sized office.